Characterization of Gadolinium Contrast Enhancement of Radiofrequency Ablation Lesions in Predicting Edema and Chronic Lesion Size

Abstract

Background MRI has been used to acutely visualize radiofrequency (RF) ablation lesions but its accuracy in predicting chronic lesion size is unknown. The main goal of this study was to characterize different areas of enhancement in late gadolinium enhancement (LGE) MRI done immediately after ablation to predict acute edema and chronic lesion size. Methods and Results In a canine model (n=10), ventricular RF lesions were created, using ThermoCool SmartTouch (Biosense Webster) catheter. All animals underwent MRI (LGE and T2-weighted (T2w) edema imaging), immediately after ablation and after 1, 2, 4 and 8 weeks. Edema, microvascular obstruction (MVO) and enhanced volumes were identified in MRI and normalized to chronic histological volume. Immediately after contrast administration, the MVO region was 3.2 +/− 1.1 times larger than the chronic lesion volume in acute MRI. Even 60 mins after contrast administration, edema was 8.73 +/− 3.31 times and the enhanced area 6.14 +/− 2.74 times the chronic lesion volume. Exponential fit to the MVO volume was found to be the best predictor of chronic lesion volume at 26.14 (95% prediction interval 24.35 – 28.11) mins after contrast injection. The edema volume in LGE correlated well with edema volume in T2w MRI with an R2 of 0.99. Conclusion MVO region on acute LGE images acquired 26.1 min after contrast administration can accurately predict the chronic lesion volume. We also show that T1-weighted MRI images acquired immediately after contrast injection accurately shows edema resulting from RF ablation.

Acute noncontrast T1‐weighted magnetic resonance imaging predicts chronic radiofrequency ablation lesions

“…Our results demonstrate that LGE images acquired about 30 minutes after injection overestimated the chronic lesion size by almost a factor of 4. More recently, it was shown that the MVO region in acute LGE‐MRI acquired at 26.1 minutes after contrast administration is a good predictor of chronic ventricular lesions …”

“…To identify such changes in tissue and evaluate lesion formation, late gadolinium enhancement magnetic resonance imaging (LGE‐MRI) has been used acutely and chronically after RF and cryoablation procedures. However, it is difficult to rely on acute LGE‐MRI to accurately predict the size of chronic lesions due to spatially and temporally nonuniform enhancement of ablated areas observed in acute LGE‐MRI …”

Higher contact force during radiofrequency ablation leads to a much larger increase in edema as compared to chronic lesion size

“…It is appealing to envison imaging approaches that could help determine extent of lesion during the procedure. Real‐time MRI techniques provide an immediate and direct means of measuring ablation‐related tissue changes in addition to improved visualization of the tissue, as shown by numerous prior studies . Despite this appeal of using MRI in real time, the techniques are still being developed and are not ready for clinical use .…”

Effect of radiofrequency on epicardial myocardium after ablation of ventricular arrhythmias from within coronary sinus

“…CMRI provides enhanced visualization of soft tissues with high spatial and temporal resolution . It can differentiate an acute edema in the setting of ablation from a chronic lesion that ultimately develops.…”